Press 
Airline miles are big business for airlines. Long gone are the days of frequent flyer programs being just a punch card to generate a little extra loyalty from flyers. Instead, airlines are now dependent on their mileage programs for survival.
American and United recently unveiled valuations of their mileage programs, and each is worth at least $20 billion. Here’s why these programs are so valuable.
Source: How Airlines Make Billions From Monetizing Frequent Flyer Programs
